Concentric stranded conductor

ABSTRACT

A concentric stranded conductor having a concentric strand having multiple bunched strands twisted together, in which each bunched strand has multiple single wires twisted together; 
     wherein the concentric stranded conductor has a central core bunched strand ( 5 ) and a first-layer concentric strand ( 11 ) having multiple first-layer bunched strands ( 9 ) twisted together around the central core bunched strand ( 5 );    wherein a twist pitch of the central core bunched strand ( 5 ) is from 8 to 70 times an outer strands distance thereof, a twist pitch of the first-layer concentric strand ( 11 ) is from 8 to 30 times an outer strands distance thereof, a difference between a twist angle of the central core bunched strand ( 5 ) and a sum of twist angles of the first-layer bunched strands ( 9 ) and first-layer concentric strand ( 11 ) is 15 degrees or less, and each single wire is made of an aluminum or aluminum alloy, having elongation of 2% or more.

TECHNICAL FIELD

This invention relates to a concentric strand excellent in flexibility,particularly to a concentric stranded conductor for electricaltransmission which is excellent in flexibility and is used forautomobiles and the like.

BACKGROUND ART

Copper has been mainly used as a material of the concentric strandedconductor (rope lay concentric conductor) for electrical transmissionused for automobiles and the like. In recent years, automobiles and thelike are required to be lightweight in view of energy-saving andenvironmental preservation, and the like. Therefore, lightening theconcentric stranded conductor for electrical transmission is one of theproblems. As a method for lightening, it has been devised use ofaluminum which has a small specific gravity, in place of copper.

An example is a concentric stranded conductor for electricaltransmission that is excellent in bending resistance and vibrationresistance and is hardly broken by friction and wearing at the time ofbending and vibration (for example, see JP-A-2003-303515 (“JP-A” meansunexamined published Japanese patent application)).

FIG. 2(a) is a partial perspective view shown by cutting a part of theconcentric stranded conductor for electrical transmission described inJP-A-2003-303515. FIG. 2(b) is a schematic cross section of theconcentric stranded conductor. The concentric stranded conductor (1) forelectrical transmission, described in JP-A-2003-303515 is a concentricstrand formed by twisting a plurality of single wires (3), (7), or (13)into a child strand (i.e. a wire construction consists of bunched orconcentric configurations), and then twisting a plurality of the childstrands. The concentric stranded conductor comprises a child strand as acenter (central core bunched strand (5) (a “bunched strand” refers to astrand containing any number of wires twisted together in the samedirection, and in a bunched strand, wires having the same lay length arelocated randomly)), a first-layer concentric strand (11) formed aroundthe child strand as a center by twisting first-layer bunched strands (9)so that the twist direction of child strand (i.e. the twisting directionof the single wires forming each child strand) is the same as the twistdirection of parent strand (herein, a “parent strand” or “rope strand”is a final bunched or concentric configuration constructed by childstrands, and “twist direction of parent strand” refers to the twistingdirection of the child strands forming the parent strand), and at leastone layer of a concentric strand (17) formed around the first-layerconcentric strand by twisting the second-layer bunched strands (15) sothat parent twist directions of adjoining layers are in the oppositedirection to one another and so that the twist direction of the childstrands of each layer is the same as the twist direction of the parentstrand.

Automobiles mounting a large capacity battery such as electric cars andhybrid cars have been developed in recent years. Aluminum concentricstranded wires are also used as a conductor for electrical transmissionfrom the battery. Since an electrical transmission amount is large inthese automobiles, a concentric stranded wire having a larger diameterthan conventional ones is used. However, there is an apprehension that alarger diameter can make attaching the concentric stranded wire to abody of automobiles difficult. In addition, a wire should be disposed ina limited space; therefore a concentric stranded conductor furtherexcellent in flexibility has been demanded.

DISCLOSURE OF INVENTION

The object of the invention is to solve the above-mentioned problems andto provide a concentric stranded conductor excellent in flexibility.

In order to solve the above-mentioned problems, the invention providesas the first embodiment, a concentric stranded conductor having aconcentric strand comprising a plurality of bunched strands twistedtogether, in which each of the bunched strands comprises a plurality ofsingle wires twisted together; wherein the concentric stranded conductorhas a central core bunched strand (5) and a first-layer concentricstrand (11) which comprises a plurality of first-layer bunched strands(9) twisted together around the central core bunched strand (5); whereina twist pitch of the central core bunched strand (5) is from 8 to 70times an outer strands distance of the central core bunched strand (5),a twist pitch of the first-layer concentric strand (11) is from 8 to 30times an outer strands distance of the first-layer concentric strand(11), a difference (expressed by an absolute value) between a twistangle of the central core bunched strand (5) and a sum of a twist angleof the first-layer bunched strands (9) and a twist angle of thefirst-layer concentric strand (11) is 15 degrees or less, and each ofthe single wires is made of aluminum or an aluminum alloy, each havingelongation of 2% or more.

The second embodiment of the invention is a concentric strandedconductor according to the first embodiment, wherein all of the centralcore bunched strand (5), the first-layer bunched strands (9), and thefirst-layer concentric strand (11) are twisted together in the sametwist direction.

The third embodiment of the invention is a method for producing aconcentric stranded conductor (1) comprising the steps of: twistingtogether, around a central core bunched strand (5), a first-layerconcentric strand (11) in the same twist direction as the twistdirection of the central core bunched strand (5), which first-layerconcentric strand (11) comprising first-layer bunched strands (9) eachtwisted together in the same twist direction as the twist direction ofthe central core bunched strand (5); and twisting together, around thefirst-layer concentric strand (11), a second-layer concentric strand(17) in the same twist direction as the twist direction of the centralcore bunched strand (5), which second-layer concentric strand (17)comprising second-layer bunched strands (15) each twisted together inthe same twist direction as the twist direction of the central corebunched strand (5); wherein the conductor uses aluminum or an aluminumalloy each having elongation of 2% or more as the single wires; whereina twist pitch of the central core bunched strand (5) is from 30 to 70times the outer strands distance of the central core bunched strand (5);wherein a twist pitch of the second-layer concentric strand (17) is from10 to 30 times the outer strands distance of the second-layer concentricstrand (17); and wherein the twist pitch of the first-layer concentricstrand (11) is the same as or larger than the twist pitch of thesecond-layer concentric strand (17) and a difference between the twistpitches is 20 or lower.

The fourth embodiment of the invention is a method for producing aconcentric stranded conductor, wherein, in the method for producing aconcentric stranded conductor according to the third embodiment,multiple layers of concentric strands, each of which comprises bunchedstrands twisted together in the same twist direction as the twistdirection of the central core bunched strand (5), are twisted togetherin the same twist direction as the twist direction of the central corebunched strand (5) around the second-layer concentric strand (17).

The fifth embodiment of the invention is a concentric stranded conductorhaving a second-layer concentric strand (17) comprising a plurality ofsecond-layer bunched strands (15) twisted together around the concentricstranded conductor according to the first or second embodiment, whereina difference between the twist angle of the central core bunched strand(5) and a sum of a twist angle of the second-layer bunched strands (15)and a twist angle of the second-layer concentric strand (17) is 15degrees or less; wherein a difference between a sum of the twist angleof the first-layer bunched strands (9) and the twist angle of thefirst-layer concentric strand (11) and a sum of the twist angle of thesecond-layer bunched strands (15) and the twist angle of thesecond-layer concentric strand (17) is 15 degrees or less; and wherein atwist pitch of the second-layer concentric strand (17) is from 8 to 30times an outer strands distance of the second-layer concentric strand(17).

The sixth embodiment of the invention is a concentric strandedconductor, wherein, in the concentric stranded conductor according tothe fifth embodiment, all of the central core bunched strand (5), thefirst-layer bunched strands (9), the first-layer concentric strand (11),the second-layer bunched strands (15), and the second-layer concentricstrand (17) are twisted in the same twist direction.

The “outer strands distance” used in the invention refers to a diameterobtained by subtracting an outer diameter of one single wire from anouter diameter of a stranded wire.

A proportion of face contact between single wires is enhanced in theinvention. Accordingly, since concentrated contact portions between thelayers as in the prior art are dispersed in the invention, local nickingdecreases and flexibility is improved due to good slidability betweensingle wires. Since the entire single wires are aligned in the sametwist direction by twisting all of bunched strands and concentricstrands in the concentric stranded conductor, the single wires arebrought into face contact and flexibility is further improved.

Other and further features and advantages of the invention will appearmore fully from the following description, appropriately referring tothe accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates a partial perspective view (a) and across section (b) of a preferred embodiment of this invention.

FIG. 2 schematically illustrates a partial perspective view (a) and across section (b) in the prior art.

FIG. 3 is a side view of a flexibility test machine used in the example.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferable modes of the invention will be described below.

The concentric stranded conductor (1) of the invention comprises aconcentric strand, which is formed by twisting together a plurality ofsingle wires into a bunched strand and then twisting together aplurality of such bunched strands. Particularly, it is preferable thatthe concentric stranded conductor (1) comprise multiple layers whereinall of the twist directions of the central core bunched strand (5), thefirst-layer bunched strands (9), the first-layer concentric strand (11),the second-layer bunched strands (15), the second-layer concentricstrand (17), are the same, i.e. all of the twist directions of bunchedstrands of each layer (“twist direction of bunched strand” refers to thetwist direction of single wires forming the bunched strand) andconcentric strands of each layer (“twist direction of concentric strand”refers to the twist direction of bunched strands forming the concentricstrand) are the same.

FIG. 1(a) is a partial perspective view shown by cutting a part of theconcentric stranded conductor (1).

FIG. 1(b) is a schematic cross section of the concentric strandedconductor (1). Each arrow in FIG. 1(b) shows the twist direction of thesingle wires (3), (7), or (13) explained below. In the concentricstranded conductor (1), a central core bunched strand (5) formed bytwisting single wires (3) together, for example, counterclockwise isplaced at the center, and six of first-layer bunched strands (9) eachformed by twisting single wires (7) together counterclockwise, aretwisted counterclockwise to form the first-layer concentric strand (11).

Then, twelve of second-layer bunched strands (15) each formed bytwisting together single wires (13) counterclockwise, are twistedcounterclockwise around the first-layer concentric strand (11) to formthe second-layer concentric strand (17). The second-layer concentricstrand (17) is coated by an insulator coating (21) so as to contact thesurface closely.

It is preferable that the twist direction of the central core bunchedstrand (5) is in the same twist direction as the twist direction of thefirst-layer concentric strand (11) provided around the central corebunched strand (5) for improving flexibility of the conductor.

The first-layer concentric strand (11) is preferably twisted together inthe same twist direction as the twist direction of the first-layerbunched strands (9). Twisting the first-layer concentric strand (11) andthe first-layer bunched strands (9) in the same twist direction to oneanother is preferable, since the single wires (7) in the first-layerbunched strands (9) are brought into face contact with one another andthe strands are twisted so that the cross sectional shape of the strandof the first-layer bunched strands (11) is deformed. In other words, bytwisting, the shape of the cross section of the first-layer bunchedstrands (9) is deformed into a trapezoid like shape (i.e. a shape thatis a remainder of subtracting a sector having an angle of 180° or lessfrom a larger similar sector), causing the adjoining first-layer bunchedstrands (9) to be brought into close contact one another, therebyreducing the gap.

The second-layer concentric strand (17) is preferably twisted in thesame twist direction as the twist direction of the second-layer bunchedstrands (15). Twisting the second-layer concentric strand (17) and thesecond-layer bunched strands (15) in the same twist direction ispreferable since the single wires (13) of the second-layer bunchedstrands (15) are brought into face contact with one another, and thesecond-layer bunched strands (15) are twisted so that the shape of thecross section of each strand is deformed.

As shown in FIG. 1(b), by twisting, the shape of the cross section ofthe second-layer bunched strands (15) is deformed into a trapezoid likeshape, causing the adjoining second-layer bunched strands (15) to bebrought into close contact with one another, thereby reducing the gap.

The twist pitch of the central core bunched strand (5) is from 8 to 70times the outer strands distance of the central core bunched strand (5),and more preferably from 10 to 30 times in order to improve flexibilityof the conductor.

The twist pitch of the first-layer concentric strand (11) is from 8 to30 times the outer strands distance of the first-layer concentric strand(11), and more preferably from 10 to 20 times in order to improveflexibility of the conductor.

The twist pitch of the second-layer concentric strand (17) is preferably8 to 30 times the outer strands distance of the second-layer concentricstrand (17) in order to improve flexibility of the conductor. The twistpitch is more preferably from 10 to 20 times. The twist pitch (seeFIG. 1) can be determined, for example, with reference to JIS G3525.

The difference (absolute value) between the twist angle of the centralcore bunched strand (5) and the sum of the twist angle of thefirst-layer bunched strands (9) and the twist angle of the first-layerconcentric strand (11) is from 15 degrees or less to 0 degree or more,more preferably from 10 degrees or less to 0 degree or more forimproving flexibility. It is also preferable for improving flexibilitythat the difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the second-layer bunchedstrands (15) and the twist angle of the second-layer concentric strand(17) is from 15 degrees or less to 0 degree or more, more preferablyfrom 10 degrees or less to 0 degree or more. In addition, the differencebetween the sum of the twist angle of the first-layer bunched strands(9) and the twist angle of the first-layer concentric strand (11) andthe sum of the twist angle of the second-layer bunched strands (15) andthe twist angle of the second-layer concentric strand (17) is from 15degrees or less to 0 degree or more for improving flexibility, morepreferably from 10 degrees or less to 0 degree or more. The twist anglerefers to an angle in the longitudinal direction of bunched strands orconcentric strands.

By forming a concentric stranded conductor (1) as shown in FIG. 1(b), itis possible to reduce roughness of the outer circumference of theconcentric stranded conductor (1). That is, while the insulator coating(21) that has been used for conventional concentric stranded conductorsmay be provided on the concentric stranded conductor (1) of theinvention by a conventional method, the insulator coating (21) does notpenetrate into the gap between the second-layer bunched strands (15).Therefore, the second-layer bunched strands (15) do not tightly contactwith the insulator coating (21).

In the following, the invention is described in more detail, but theinvention is not restricted thereto.

In the concentric stranded conductor (1), for example, the central corebunched strand (5) formed by twisting thirteen aluminum single wires (3)with a diameter of 0.32 mm together in a counterclockwise direction, isplaced at the center, and six first-layer bunched strands (9) formed bytwisting thirteen aluminum single wires (7) with a diameter of 0.32 mmtogether in a counterclockwise direction, are twisted together in acounterclockwise direction to form the first-layer concentric strand(11).

The twist direction of the first-layer concentric strand (11) ispreferably the same as the twist direction of the first-layer bunchedstrands (9). Twisting in the same twist direction is preferable sincethe single wires (7) of the first-layer bunched strands (9) are broughtinto face contact with one another, causing the first-layer bunchedstrands (9) to be twisted so that the shape of the cross section of eachstrand is deformed. As shown in FIG. 1(b), by twisting, the shape of thecross section of the first-layer bunched strands (9) is deformed into atrapezoid like shape, causing the adjoining first-layer bunched strands(9) to be brought into close contact with one another, thereby reducingthe gap.

The central core bunched strand (5) is preferably bunched stranded inthe same twist direction for improving flexibility. The bunchedstranding in the same twist direction may be conducted using a buncherstrander. The first-layer concentric strand (11) and the second-layerconcentric strand may be twisted using a planetary strander (withstrand-back) or rigid strander (without strand-back).

A second-layer concentric strand (17) is preferably disposed around thefirst-layer concentric strand (11). Such a second-layer concentricstrand (17) is formed by using second-layer bunched strands (15) formedby using thirteen single wires (13) twisted together counterclockwise,and by stranding twelve of such second-layer bunched strands (15)counterclockwise.

Twisting the second-layer concentric strand (17) and the second-layerbunched strands (15) in the same twist direction to one another ispreferable, since the single wires (13) of the second-layer bunchedstrands (15) are brought into face contact with one another, and thesecond-layer bunched strands (15) are twisted so that the crosssectional shape of each strand is deformed.

Concentric strands having bunched strands with a deformed crosssectional shape are able to have a smaller outer diameter as well as asmaller outer diameter of a coating, as compared with conventionalstructures. Further, since the surface roughness is reduced, the ratioof the thickness of the insulator coating (21) (roughness of the innersurface of the insulator coating) can be reduced, and this enables anamount of the coating material to be reduced.

According to the invention, because the roughness of the outercircumference of the concentric stranded conductor (1) is reduced, theinsulator coating (21) scarcely penetrates into the gaps around thesecond-layer concentric strand (17). Accordingly, a concentration of anadhesive force may be relaxed since the adhesive force between theinsulator coating (21) and the concentric stranded conductor (1) isshared by the concentric stranded conductor (1). Consequently, theconductor becomes easy to bend (good flexibility) and slidability isimproved, resulting in improvement of bending resistance and wearresistance.

According to the invention, the single wires (7) and single wires (13)are brought into face contact with one another. Consequently, localnicking is reduced since concentrated contact parts among the layers aredispersed, resulting in improvement of bendability and slidability aswell as improvement of bending resistance and wear resistance.

According to the invention, since crossover between single wires isreduced inside a terminal, nicking of single wires is reduced andtherefore the deterioration of strength of the electrical wire at thetime of solderless connection or weld connection is reduced.

The invention is by no means restricted to the modes of the invention,and may be implemented in various embodiments unless which deviates fromthe gist of the invention. For example, while the twist direction iscounterclockwise in the above-mentioned modes, the twist direction maybe clockwise.

The conductor of the invention is preferably formed by coating theconcentric stranded conductor (1), which comprises single wires (3),(7), and (13) of aluminum or aluminum alloy, with the insulator coating(21). The single wires (3), (7), and (13) preferably have elongation of2% or more because this improves flexibility. The elongation is morepreferably 5% or more and is further preferably 15% or more. As thealuminum or aluminum alloy, any aluminum or aluminum alloy can be usedas long as it can be processed into the single wires (3), (7), and (13),and the aluminum alloy is not particularly restricted by its alloycomponent.

In the following, preferable embodiments when preparing the concentricstranded conductors of the invention as concentric stranded conductorsfor electrical transmission for automobiles and the like will bedescribed below.

While the diameter of the single wire is not particularly restricted, itis usually from 0.16 mm to 1.0 mm, preferably about 0.3 mm. While thenumber of the single wires constituting the central core bunched strandis not particularly restricted, it is usually from 7 to 80 single wires,preferably from 10 to 30 single wires. While the number of the singlewires constituting bunched strands in the n-th layer (n is an integer of1 or more) is not particularly restricted, it is usually from 7 to 80single wires, preferably from 10 to 30 single wires. While the number ofthe bunched strands constituting the n-th layer concentric strand (n isan integer of 1 or more) is not particularly restricted, it is usuallyfrom 6 to 80 strands, preferably from 7 to 80 strands, and morepreferably from 10 to 30 strands. While the number of concentric strandlayer is not particularly restricted, it is usually from 1 to 3 layers,more preferably from 2 to 3 layers.

As the insulator coating, those generally used for conventionalconcentric stranded conductors may be used, and it is preferably apolyethylene resin or a noryl resin.

In the following, the present invention will be described in more detailbased on examples, but the invention is not meant to be limited bythese.

EXAMPLES

As the examples of the invention, concentric stranded conductors wereproduced in the following procedures, using a strander. Firstly, acentral core bunched strand (5) formed by twisting thirteen aluminumsingle wires (3) with a diameter of 0.32 mm together in acounterclockwise direction was placed at the center, and six offirst-layer bunched strands (9) each formed by twisting thirteenaluminum single wires (7) with a diameter of 0.32 mm together in acounterclockwise direction, were twisted counterclockwise to form afirst-layer concentric strand (11). In Examples 16 to 24, these wereused as concentric stranded conductors, without further modification.

In Examples 1 to 15, the second-layer bunched strands (15) were formedby twisting thirteen aluminum single wires (13) together, and thesecond-layer concentric strand (17) was formed by twisting twelvesecond-layer bunched strands (15) counterclockwise around thefirst-layer concentric strand (11). For the purpose of comparison,Comparative Examples 1 to 22 were prepared with appropriately changingthe kind of the strand, the twist angle, and the twist pitch.

The prepared concentric stranded conductors (1) were evaluated using aflexibility test apparatus (51) as shown in FIG. 3. Five concentricstranded conductors (1) with a length of 150 mm and a cross section of20 mm² were prepared with respect to each example and comparativeexample. A 160 g weight (57) was attached at one end of each concentricstranded conductor (1), and the other end of the concentric strandedconductor (1) was fixed on a mandrel (53) with a diameter of 90 mm,using a conductor fixing fitting (55). The horizontal distance betweenone end (the side to which the weight (57) was attached) of theconcentric stranded conductor (1) and mandrel 53 was measured as anamount of displacement, L, and it was judged that the smaller the amountof displacement L the better flexibility (the concentric strandedconductors which had an amount of displacement of 30 mm or less werejudged to be successfully flexible). The test was repeated five times bychanging the concentric stranded conductors (1), and the results werecompared among the examples or comparative examples using the averagevalue of the amount of displacement. As to Examples 16 to 24 andComparative Examples 18 to 22, the measuring conditions were the same asdescribed above, except that these conductors were measured for amountof displacement with using a 60-g weight in place of the 160-g weight.The results of comparison are shown in Tables 1 and 2. In the following,“Twist pitch magnification” in Tables 1 and 2 is represented by a ratioof “pitch (mm)/outer strands distance)” (i.e. twisting pitch in lengthdivided by strand diameter). TABLE 1 Single Central core bunchedFirst-layer bunched First-layer concentric wire strand strands strandelongation Twist Pitch Twist pitch Twist Pitch Twist pitch Twist PitchTwist pitch (%) angle (mm) magnification angle (mm) magnification angle(mm) magnification Example 1 5 4.1 43.4 33.0 4.1 43.4 33.0 8.9 52.6 20.02 5 2.0 89.4 68.0 2.0 89.4 68.0 8.9 52.6 20.0 3 5 2.7 65.8 50.0 2.7 65.850.0 6.0 78.9 30.0 4 5 2.7 65.8 50.0 2.7 65.8 50.0 6.0 78.9 30.0 5 122.7 65.8 50.0 2.7 65.8 50.0 6.0 78.9 30.0 6 17 2.7 65.8 50.0 1.9 92.170.0 6.0 78.9 30.0 7 2 2.7 65.8 50.0 4.5 39.5 30.0 6.0 78.9 30.0 8 2 4.143.4 33.0 4.1 43.4 33.0 8.9 52.6 20.0 9 2 2.0 89.4 68.0 2.0 89.4 68.08.9 52.6 20.0 10 2 2.0 89.4 68.0 −4.9 −36.8 28.0 6.0 78.9 30.0 11 2 4.936.8 28.0 4.9 36.8 28.0 8.9 52.6 20.0 12 2 4.9 36.8 28.0 −4.9 −36.8 28.017.4 26.3 10.0 13 2 4.9 36.8 28.0 4.9 36.8 28.0 8.9 52.6 20.0 14 2 4.936.8 28.0 13.4 13.2 10.0 −8.9 −52.6 20.0 15 2 6.8 26.3 20.0 4.9 36.828.0 −8.9 −52.6 20.0 Comparative example 1 5 4.1 43.4 33.0 4.1 43.4 33.08.9 52.6 20.0 2 5 1.8 98.6 75.0 1.8 98.6 75.0 8.9 52.6 20.0 3 5 2.7 65.850.0 2.7 65.8 50.0 5.1 92.1 35.0 4 5 2.7 65.8 50.0 −4.5 −39.5 30.0 3.7128.9 49.0 5 5 −4.9 −36.8 28.0 −4.9 −36.8 28.0 6.0 78.9 30.0 6 5 2.765.8 50.0 16.5 10.5 8.0 9.4 50.0 19.0 7 1.5 2.7 65.8 50.0 2.7 65.8 50.06.0 78.9 30.0 8 5 −2.7 −65.8 50.0 6.8 26.3 20.0 6.0 78.9 30.0 9 5 2.765.8 50.0 −6.8 −26.3 20.0 −6.0 −78.9 30.0 10 5 2.7 65.8 50.0 6.8 26.320.0 −6.0 −78.9 30.0 11 5 −2.7 −65.8 50.0 −2.7 −65.8 50.0 −6.0 −78.930.0 12 1.5 4.9 36.8 28.0 4.9 36.8 28.0 8.9 52.6 20.0 13 1.5 6.8 26.320.0 4.9 36.8 28.0 −8.9 −52.6 20.0 14 2 17.6 9.9 7.5 17.6 9.9 7.5 9.450.0 19.0 15 5 13.4 13.2 10.0 1.9 92.1 70.0 22.7 19.7 7.5 16 5 4.9 36.828.0 4.9 36.8 28.0 9.4 50.0 19.0 17 5 4.9 36.8 28.0 4.9 36.8 28.0 9.450.0 19.0 Second-layer bunched Second-layer strands concentric strandTwist Pitch Twist pitch Twist Pitch Twist pitch angle (mm) magnificationangle (mm) magnification Example 1 4.1 43.4 33.0 14.7 63.1 12.0 2 2.089.4 68.0 14.7 63.1 12.0 3 −2.3 −78.9 60.0 14.7 63.1 12.0 4 6.8 26.320.0 6.2 152.6 29.0 5 2.7 65.8 50.0 8.9 105.2 20.0 6 −1.9 −92.1 70.0 8.9105.2 20.0 7 4.5 39.5 30.0 8.9 105.2 20.0 8 −4.1 −43.4 33.0 14.7 63.112.0 9 2.0 89.4 68.0 14.7 63.1 12.0 10 4.9 36.8 28.0 6.2 152.6 29.0 114.9 36.8 28.0 −6.0 −157.8 30.0 12 4.9 36.8 28.0 6.0 157.8 30.0 13 4.936.8 28.0 6.0 157.8 30.0 14 4.9 36.8 28.0 6.0 157.8 30.0 15 4.9 36.828.0 6.0 157.8 30.0 Comparative example 1 4.1 43.4 33.0 19.2 47.4 9.0 21.8 98.6 75.0 14.7 63.1 12.0 3 2.7 65.8 50.0 14.7 63.1 12.0 4 4.5 39.530.0 5.6 168.4 32.0 5 4.9 36.8 28.0 8.9 105.2 20.0 6 2.7 65.8 50.0 8.9105.2 20.0 7 16.5 10.5 8.0 8.9 105.2 20.0 8 6.8 26.3 20.0 8.9 105.2 20.09 −6.8 −26.3 20.0 8.9 105.2 20.0 10 −4.5 −39.5 30.0 −8.9 −105.2 20.0 114.5 39.5 30.0 8.9 105.2 20.0 12 4.9 36.8 28.0 −6.0 −157.8 30.0 13 4.936.8 28.0 6.0 157.8 30.0 14 17.6 9.9 7.5 6.0 157.8 30.0 15 4.5 39.5 30.06.0 157.8 30.0 16 4.9 36.8 28.0 22.7 39.5 7.5 17 −4.9 −36.8 28.0 5.6168.4 32.0 Difference of the twist angle Amount of ※1 (First layer ※2(Second ※3 (First layer and displacement and center) layer and center)second layer) (mm) Example 1 8.9 14.7 5.7 22 2 8.9 14.7 5.7 28 3 6.0 9.73.7 20 4 6.0 10.2 4.3 26 5 6.0 8.9 2.9 13 6 5.2 4.3 0.9  9 7 7.8 10.72.9 22 8 8.9 6.4 2.5 20 9 8.9 14.7 5.7 26 10 0.9 9.0 9.9 24 11 8.9 6.014.9 30 12 7.7 6.0 1.8 15 13 8.9 6.0 2.9 22 14 0.4 6.0 6.4 18 15 10.94.1 14.9 30 Comparative example 1 8.9 19.2 10.3 ★1 2 8.9 14.7 5.7 36 35.1 14.7 9.5 35 4 3.6 7.4 11.0 35 5 6.0 18.6 12.7 ★1 6 23.2 8.9 14.3 ★17 6.0 22.8 16.8 39 8 15.5 18.4 2.9 40 9 15.5 0.6 14.9 36 10 1.9 16.214.3 40 11 6.0 16.2 22.2 35 12 8.9 6.0 14.9 32 13 10.9 4.1 14.9 33 149.4 6.0 3.4 ★1 15 11.3 2.9 14.2 35 16 9.4 22.7 13.3 40 17 9.4 4.1 13.533Note 1:As to the twist direction, counterclockwise twisting and clockwisetwisting are shown by + and −, respectively.★1: A conductor cannot be manufactured since concentric stranding wasimpossible.※1: The value indicates the difference between the twist angle of thecentral core bunched strand (5) and the sum of the twist angle of thefirst-layer bunched strands (9) and the twist angle of first-layerconcentric strand (11).※2: The value indicates the difference between the twist angle of thecentral core bunched strand (5) and the sum of the twist angle of thesecond-layer bunched strands (15) and the twist angle of second-layerconcentric strand (17).※3: The value indicates the difference between the sum of the twistangle of the first-layer bunched strands (9) and the twist angle of thefirst-layer concentric strand (11) and the sum of the twist angle of thesecond-layer bunched strands (15) and the twist angle of thesecond-layer concentric strand (17).

TABLE 2 Difference Single of the wire Central core bunched strandFirst-layer bunched strands First-layer concentric strand twist Amountof elongation Twist Pitch Twist pitch Twist Pitch Twist pitch TwistPitch Twist pitch angle displacement (%) angle (mm) magnification angle(mm) magnification angle (mm) magnification ※1 (mm) Example 16 2 4.936.8 28.0 4.9 36.8 28.0 9.4 50.0 19.0 9.4 16 Example 17 2 16.5 10.5 8.04.9 36.8 28.0 9.4 50.0 19.0 2.3 10 Example 18 2 2.1 85.5 65.0 4.9 36.828.0 9.4 50.0 19.0 12.1 19 Example 19 2 4.9 36.8 28.0 4.9 36.8 28.0 6.473.7 28.0 6.4 16 Example 20 2 9.0 19.7 15.0 1.9 92.1 70.0 21.4 21.0 8.014.4 20 Example 21 2 4.9 36.8 28.0 4.9 36.8 28.0 7.2 65.8 25.0 7.2 15Example 22 2 4.9 36.8 28.0 −4.9 −36.8 −28.0 9.4 50.0 19.0 0.3 10 Example23 2 4.9 36.8 28.0 4.9 36.8 28.0 −9.4 −50.0 19.0 9.4 17 Example 24 2−2.1 −85.5 65.0 4.9 36.8 28.0 6.4 73.7 28.0 13.3 20 Comparative 2 1.898.6 75.0 4.9 36.8 28.0 9.4 50.0 19.0 12.4 ★1 example 18 Comparative 218.8 9.2 7.0 4.9 36.8 28.0 9.4 50.0 19.0 4.5 ★1 example 19 Comparative 24.9 36.8 28.0 4.9 36.8 28.0 24.2 18.4 7.0 24.2 22 example 20 Comparative2 4.9 36.8 28.0 4.9 36.8 28.0 5.6 84.2 32.0 5.6 ★1 example 21Comparative 2 9.0 19.7 15.0 4.9 36.8 28.0 21.4 21.0 8.0 17.3 21 example22Note 1:As to the twist direction, counterclockwise twisting and clockwisetwisting are shown by + and −, respectively.★1: It was impossible to manufacture a conductor, since concentricstranding was impossible.※1: The value indicates the difference between the twist angle of thecentral core bunched strand (5) and the sum of the twist angle of thefirst-layer bunched strands (9) and the twist angle of the first-layerconcentric strand (11).

As is apparent from Tables 1 and 2, the examples according to theinvention exhibited small amount of displacement and were excellent inflexibility.

On the contrary, with Comparative Example 1, concentric stranding wasimpossible since the difference between the twist angle of the centralcore bunched strand (5) and the sum of the twist angle of thesecond-layer bunched strands (15) and the twist angle of thesecond-layer concentric strand (17) exceeded 15 degrees.

Comparative Example 2 exhibited a large amount of displacement, sincethe twist pitch of the central core bunched strand (5) exceeded 70 timesthe outer strands distance of the central core bunched strand (5).

Comparative Example 3 exhibited a large amount of displacement, sincethe twist pitch of the first-layer concentric strand (11) exceeded 30times the outer strands distance of the first-layer concentric strand(11).

Comparative Example 4 exhibited a large amount of displacement, sincethe twist pitch of the first-layer concentric strand (11) exceeded 30times the outer strands distance of the first-layer concentric strand(11) and the twist pitch of the second-layer concentric strand exceeded30 times the outer strands distance of the second-layer concentricstrand.

With Comparative Example 5, concentric stranding was impossible, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the second-layer bunchedstrands (15) and the twist angle of the second-layer concentric strand(17) exceeded 15 degrees.

With Comparative Example 6, concentric stranding was impossible, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the first-layer bunchedstrands (9) and the twist angle of the first-layer concentric strand(11) exceeded 15 degrees.

Comparative Example 7 exhibited a large amount of displacement, sincethe elongation of the strands was less than 2% and the differencebetween the twist angle of the central core bunched strand (5) and thesum of the twist angle of the second-layer bunched strands (15) and thetwist angle of the second-layer concentric strand (17) exceeded 15degrees.

Comparative Example 8 exhibited a large amount of displacement, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the first-layer bunchedstrands (9) and the twist angle of the first-layer concentric strand(11) exceeded 15 degrees.

Comparative Example 9 exhibited a large amount of displacement, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the first-layer bunchedstrands (9) and the twist angle of the first-layer concentric strand(11) exceeded 15 degrees.

Comparative Example 10 exhibited a large amount of displacement, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the second-layer bunchedstrands (15) and the twist angle of the second-layer concentric strand(17) exceeded 15 degrees.

Comparative Example 11 exhibited a large amount of displacement, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the second-layer bunchedstrands (15) and the twist angle of the second-layer concentric strand(17) exceeded 15 degrees, and since the difference between the sum ofthe twist angle of the first-layer bunched strands (9) and the twistangle of the first-layer concentric strand (11) and the sum of the twistangle of the second-layer bunched strands (15) and the twist angle ofthe second-layer concentric strand (17) exceeded 15 degrees.

Comparative Example 12 exhibited a large amount of displacement, sincethe elongation of single wires was less than 2%.

Comparative Example 13 exhibited a large amount of displacement, sincethe elongation of single wires was less than 2%.

With Comparative Example 14, concentric stranding was impossible, sincethe twist pitch of the central core bunched strand (5) was less than 8times the outer strands distance of the central core bunched strand (5).

Comparative Example 15 exhibited a large amount of displacement, sincethe twist pitch of the first-layer concentric strand (11) was less than8 times the outer strands distance of the first-layer concentric strand(11).

Comparative Example 16 exhibited a large amount of displacement, sincethe twist pitch of the second-layer concentric strand was less than 8times the outer strands distance of the second-layer concentric strand,and since the difference between the twist angle of the central corebunched strand (5) and the sum of the twist angle of the second-layerbunched strands (15) and the twist angle of the second-layer concentricstrand (17) exceeded 15 degrees.

Comparative Example 17 exhibited a large amount of displacement, sincethe twist pitch of the second-layer concentric strand exceeded 30 timesthe outer strands distance of the second-layer concentric strand.

With Comparative Example 18, concentric stranding was impossible, sincethe twist pitch of the central core bunched strand (5) exceeded 70 timesthe outer strands distance of the central core bunched strand (5).

With Comparative Example 19, concentric stranding was impossible, sincethe twist pitch of the central core bunched strand (5) was less than 8times the outer strands distance of the central core bunched strand (5).

Comparative Example 20 exhibited a large amount of displacement, sincethe twist pitch of the first-layer concentric strand (11) was less than8 times the outer strands distance of the first-layer concentric strand(11).

With Comparative Example 21, concentric stranding was impossible, sincethe twist pitch of the first-layer concentric strand (11) exceeded 30times the outer strands distance of the twist pitch of the first-layerconcentric strand (11).

Comparative Example 22 exhibited a large amount of displacement, sincethe difference between the twist angle of the central core bunchedstrand (5) and the sum of the twist angle of the first-layer bunchedstrands (9) and the twist angle of the first-layer concentric strand(11) exceeded 15 degrees.

INDUSTRIAL APPLICABILITY

The invention is a concentric strand excellent in flexibility, and issuitably used as a concentric stranded conductor for electricaltransmission that is excellent in flexibility and that can be used forautomobiles, and the like.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

This non-provisional application claims priority on Patent ApplicationNo. 2004-312575 filed in Japan on Oct. 27, 2004, and Patent ApplicationNo. 2005-288978 filed in Japan on Sep. 30, 2005, each of which isentirely herein incorporated by reference.

1. A concentric stranded conductor having a concentric strand comprisinga plurality of bunched strands twisted together, in which each of thebunched strands comprises a plurality of single wires twisted together;wherein the concentric stranded conductor has a central core bunchedstrand (5) and a first-layer concentric strand (11) which comprises aplurality of first-layer bunched strands (9) twisted together around thecentral core bunched strand (5); wherein a twist pitch of the centralcore bunched strand (5) is from 8 to 70 times an outer strands distanceof the central core bunched strand (5), a twist pitch of the first-layerconcentric strand (11) is from 8 to 30 times an outer strands distanceof the first-layer concentric strand (11), a difference between a twistangle of the central core bunched strand (5) and a sum of a twist angleof the first-layer bunched strands (9) and a twist angle of thefirst-layer concentric strand (11) is 15 degrees or less, and each ofthe single wires is made of aluminum or an aluminum alloy, each havingelongation of 2% or more.
 2. The concentric stranded conductor accordingto claim 1, wherein all of the central core bunched strand (5), thefirst-layer bunched strands (9), and the first-layer concentric strand(11) are twisted in the same twist direction.
 3. A concentric strandedconductor having a second-layer concentric strand (17) comprising aplurality of second-layer bunched strands (15) twisted around theconcentric stranded conductor as claimed in claim 1 or 2, wherein adifference between the twist angle of the central core bunched strand(5) and a sum of a twist angle of the second-layer bunched strands (15)and a twist angle of the second-layer concentric strand (17) is 15degrees or less, a difference between a sum of the twist angle of thefirst-layer bunched strands (9) and the twist angle of the first-layerconcentric strand (11) and a sum of the twist angle of the second-layerbunched strands (15) and the twist angle of the second-layer concentricstrand (17) is 15 degrees or less, and a twist pitch of the second-layerconcentric strand (17) is from 8 to 30 times an outer strands distanceof the second-layer concentric strand (17).
 4. The concentric strandedconductor according to claim 3, wherein all of the central core bunchedstrand (5), the first-layer bunched strands (9), the first-layerconcentric strand (11), the second-layer bunched strands (15), and thesecond-layer concentric strand (17) are twisted in the same twistdirection.